Which Sim card + Internet pack for rare use, but long validity?

AIS, Dtac, or?

What I want:

A new Prepaid Sim Card for my "car tablet", mainly for rare Internet use (Internet radio sometimes, Google maps, Webbrowser)

Since I don't use this tablet for phone calls and don't want to top it up permanently, a long sim validity period is important.

Internet pack should be booked on demand (daily/weekly base), no monthly subscription!

I don't need any fancy LTE options, simple 3G is ok.

I checked AIS + Dtac websites, but it's little bit confusing for me.

Too many packs, options, promotions, etc. p.p.

Thanks in advance.